History:
Villain is a dealer. Kind of a bad loose-aggro type. He's been drinking. My image is probably LAGTAG-ish; villain's been commenting that I've raised 5 hands in a row. Seems like he's trying to pick a bone with me and just wants to raise/3bet if I enter the pot.

Super close on the turn under that assumption because you're oop you probably have RIO on the turn and river action. Pwning people with light showdowns is great but I think you do just fine folding this hand ott when your pf range is so strong and villain aggros back at you.

Question(s): Is it correct to say I need 20% equity to call-down profitably from turn? (pay 2 BB to win a final pot of 8BB)

It's sort of correct. As you noted, there's another player that's all-in for about 2 SB = 1 BB. This means that 3 BB of the 8 BB pot you're looking at is 3-way and you're only HU for 5 BB. Here's your share of the pot:

[Equity] = 5 * [HU % equity] + 3 * [3-way % equity]

There's a nice little mathematical shortcut here, which is that your 3-way equity only goes down from the times you beat villain but lose to all-in. So [3-way % equity] is [HU % equity] - [% beat villain and lose to AI]. A little bit of algebra and you get

[Equity] = 8 * [HU % equity] - 3 * [% beat villain and lose to AI]

Now, who knows what that value is. But whatever it is, it's smaller than your % beat villain, which is already a small number because you're bluff-catching. We'll look at this again later.

It's already been noted that the 85% range is pretty optimistic in terms of what villain might be doing. It helps sometimes to do a high and low estimate to see how elastic or inelastic the numbers are. Here's a 50% range, with the tables put side-by-side for easy comparison.

Notice how stable things are on the turn. That's because there are a lot of junk hands floating around in that bottom 35% of his range. You're adding in a lot of Qx/Jx/Tx hands that you're beating at the same time you're adding in 7x/6x/5x hands that are beating you.

There's a pretty significant difference now. You do better against the smaller range because now all those random Qx/Jx/Tx hands have made a bunch of pairs and straights and you're now glad to see them not in the range. (Any 3, 4, 5, 6, 7, 8, or K beats you. Notice how many more bad cards there are and how many of those formerly junky hands got there.)

Back to your equity: On the turn, we might estimate your HU equity to be somewhere close to 33%*. Ignoring the all-in, you're looking pretty good. We can try to factor in the all-in. Let's estimate that he's taking 50% of your wins away from you and see what happens. 50% of 33% = 16.5%. This decreases your equity from 2.64 (33% of 8 BB) to 2.15 (33% of 8 - 16.5% of 3). That changes your % equity from 33% to 27%. But in both cases, it's above the 20% for a blind calldown.

(* Note: Munga's calculation has your equity down in the 20% range. I may be reading the range wrong, but it looks like his range is suggesting that villain would be giving up on hands with no pair/no draw. That's entirely plausible and worth considering. In two of the three hands you posted, villain had a piece of the flop. In the third case, it was a paired ragged flop. Also, none of those were 3-bet hands.)

But given that the pessimistic Munga range is borderline and the optimistic range says it's fine, it's probably fine to call down.

And (perhaps counter-intuitively) you would actually prefer his range to be slightly narrower for this particular river if he's betting everything he's got. You would much prefer his range be biased more mid-range connected stuff (like J9) than high-low combos (like Q4).